Other Geohazard

Ground gases are natural gases generated by various processes including material decay (natural and anthropogenic) and magma bodies (adapted from UK HMRC, 2016 and USGS, no date). 

River erosion is the removal of material from the banks and beds of rivers and streams (cf. Lawler, 1993). River accretion is the formation of new land such as channel bars, sandbanks and deltas by sedimentation or changing river flow (after Islam and Guchhait, 2020 and Hasanuzzaman et al., 2024). 

Sand encroachment is the accumulation of wind-borne sand. It commonly affects coasts, watercourses, and both cultivated and uncultivated land, typically occurring in arid to semi-arid regions. As sand accumulations move, they can bury towns, roads, oases, crops, market gardens, irrigation channels, and dams, leading to significant material and socioeconomic damage (cf. FAO, 2010). 

Soil degradation is defined as a change in soil health status resulting in a diminished capacity of the ecosystem to provide goods and services for its beneficiaries (FAO, 2020).

Compressive soils are prone to volumetric change when subject to mechanical loading (USDA, 1990:30). Collapsible soils are metastable in that they are prone to volumetric change (collapse) on wetting and loading (Rogers, 1995). 

Erosion is the wearing away of the land surface by water, wind, ice, gravity or other natural or anthropogenic agents that abrade, detach and remove soil particles from one point on the earth's surface, for deposition elsewhere. Four main forms are recognized: water, wind, harvest and tillage. (FAO, 2020). 

Coastal erosion is the process of removal of material at the shoreline which leads to the loss of land as the shoreline retreats landward.  Coastal accretion is the product of deposition of material at the shoreline which leads to gain of land as the coast advances seaward (Gibb, 1978). 

Surface ruptures and fissures are localized ground displacements that develop in response to tensional, compressional, and shear stresses, most commonly in unconsolidated sediment, but also in rock (Arizona Geological Survey, 2020). Surface ruptures represent the upward continuation of fault slip at depth, while fissures are smaller displacements, or more distributed deformation in and around the rupture area (adapted from USGS, no date and PNSN, no date).